Ramakrishna Vikas Sadanand

The Garment manufacturing industry is facing several challenges in meeting its customer requirements due to uncertainties associated with production. Varieties of products that include many components to be produced on different machines having variations in terms of due dates and labour productivity which would make the job shop complicated for scheduling. Hence, an investigation is necessary to evaluate the influence of above underlying factors on the shop’s performance. The conceptual model was initially developed, that represents the problem entity followed by the development of a simulation model on a discrete event simulation platform. The resource capacity, process timings and other related data required for feeding the model were collected through process observation techniques. The model was then validated by conducting sensitivity analysis for evaluating the model structure, logic, and causal relationships. Artificial scenarios were generated to experiment with the model performance that mimics real time situations in terms of varying the fill rate and workload norms at distinct levels. Effectiveness of order release policies and priority dispatching rules were monitored by conducting 90 experiments determined through design of experiments. Influence of the workload control methods were evaluated through Analysis of Variance techniques to understand the percentage contribution of each variable on performance. The influence of these variables on different output measures was evaluated through Tukey tests. The experimentation revealed that flowtime is influenced to the extent of 59.72 percent by workload norms and order release methods have 59.2 percent influence on throughput.

The rotor blade manufacturing industry struggles to devise precise planning and scheduling approaches due to uncertainties in production situations. Bottleneck workloads, process time variations and re-entrant flows with varied arrival frequencies would interrupt production schedules and adversely affect the shop’s performance. Hence, an attempt has been made to study the significant impact of disproportionate workloads and the influence of innovative order release methods integrated with capacity adjustment features to enhance performance. The rotor blade manufacturing process has been thoroughly observed to incorporate the uncertain events that cause disturbance in production. A simulation model was created on a discrete event simulation platform incorporating problem phenomena through the conceptualization phase. The randomness present in the process was assessed using an input modelling approach which has resulted in probabilistic equations. The model has been verified and validated to ensure accuracy and was then subjected to 576 experimentations representing different scenarios that occur in a flow shop. Relevant workload control policies are executed to judge their effectiveness followed by Analysis of Variance Techniques. In addition, order release methods were ranked with the help of Tukey’s tests for contribution computation. Outcomes of experimentations revealed that order release methods have a major share of 80.2 percent to the throughput and 42.84 percent to flow time performance indicating the benefits of workload control strategies in decision-making during uncertain situations.

The present study involves the fabrication of aluminium alloy 6061 matrix hybrid composites with varying weight fractions of silica sand and copper particles by employing the conventional stir casting method. The combined influence of age hardening (AH) and low temperature thermomechanical treatment (LTMT) on the hardness and tensile properties of AA6061 hybrid composites was investigated. The uniform dispersion of the particles in the matrix was confirmed by microstructure analysis and the improvement of Brinell hardness values. The composites exhibited higher tensile strength and hardness than the base alloy. Both AH and LTMT enhanced the properties of the hybrid composites and a comparison between them revealed the best results for LTMT hybrid composites. The LTMT hybrid composite with 3 wt% silica sand and 3 wt% copper (3S3C) subjected to 12% rolling deformation and aged at 100 °C had the highest hardness and tensile strength of 144.26 HV and 290 MPa respectively. The hardness and tensile strength of AA6061-3S3C hybrid composite subjected to LTMT in peak aged condition showed an improvement of 125 and 97% respectively when compared with those of AA6061 alloy. Fracture surface analysis of the thermomechanical treated composites in peak aged condition showed a mixed mode of failure dominant with the ductile fracture.

The current work focuses on the natural aging phenomenon of a eutectoid steel powder-(0.8 wt.%) reinforced Al-Zn-Mg (Al 7075) alloy, which was subjected to a hybrid heat treatment. The hybrid treatment comprises the aging treatment of a matrix and the conventional treatment of a steel reinforcement in a single stretch on the stir cast composite. This material finds uses in space and transportation applications. The hybrid treatment consists of a conventional heat treatment cycle to obtain pearlite, bainite, and martensite phases in steel powder, followed by an age-hardening treatment for the Al 7075 matrix. This hybrid heat treatment resulted in improvements in the hardness and strength over the conventional aging treatment. The peak-aged hybrid specimens were subjected to natural aging in an open atmosphere for a continuous duration of 25 weeks to study the stability of the properties after peak aging. Tests of the mechanical properties such as the hardness and tensile strength along with microstructure analysis were carried out. During natural aging, the hardness of composites decreases irrespective of the quantity of the reinforcement in the composites and the type of reinforcement phase alteration during hybrid heat treatment. Also, the composites subjected to hybrid heat treatment show better resistance to natural aging compared to the conventionally aged samples. Within the group, the hybrid-treated martensite formed into a composite with 6 wt.% reinforcement showed only a 4% reduction in hardness during natural aging, which is an indication of a decent level of resistance to natural aging.